Firstly, I am new to Bettas, and to be honest, I never expected to own fish. I originally 'rescued' a typical half-dead male betta from a wal-mart to take to school as a class pet to have for our two month long science unit on fish (which requires observing fish, caring for fish, etc..) I didn't want to buy anything fancy (or expensive) because I knew I was taking it into a room full of 35 five year olds. The science teacher convinced me to do this. I didn't want a 'commitment' but she convinced me that I could always send the fish home with a willing family, and after securing said willing family I purchased Flick.

Flick now lives happily in my classroom (well, as happily as any fish can be after a child has read it 'Rainbow Fish' for the millionth time--it's kind of funny actually, because Flick flares at the foil scales on some of the pages and the kids think he's responding to the story itself) in a 1.5 gallon tank (small, I know, but the room is really cramped and a full blown tank is out of the question, we are religious about his water changes and remove organic waste with a turkey baster in between changes to help keep his environment clean) and eats a rotation of three kinds of food (for variety). But enough about Flick since he's not the subject of the question.

The point is that I feel in love with Flick, but knew I had to give him up at the end of the science unit (I made a promise after all). So I eventually went out and purchased one for myself. This time from Petco (along with a large filtered-heated-happy-betta-home). He's a different breed--delta tail? Or something to that effect--and his personality is way different.

Flick never hunted his food. He just kind of passively gobbled up his food pellets or freeze dried blood worms, or whatever and then slept on top of his silk flowers for a bit. Ninja (as I've come to call him) actually stalks his food.

He sneaks up really slowly, keeping to the cover of the aquarium plants which most closely match his color, and when he's almost nose to nose with the defenseless freeze dried morsel, he makes a fast and furious attack, twirling and jumping out of the water slightly, then plummets to the bottom of the tank to consume his prey before repeating this process with other pieces of food. I've never seen anything like it. He acts like he's in the wild, actually hunting.

I was thinking he might like some live food to 'hunt' but I wasn't sure what kind would give him the best hunting challenge yet still be safe enough for him to eat? I want him to be as happy as possible, and I know that, in zoos at least, occasional live prey and interesting eating challenges help keep carnivores from getting bored. Any suggestions?

Live brine shrimp is one possible treat, they tend to be fairly healthy for the bettas. They will eat BBS (baby brine shrimp, aka freshly hatched) but it tends to not excite them as much as when you let the brine shrimp grow up a little bit more. Grindal worms and black worms are also popular culture favorites I hear.
I use mosquito larvae myself, but admittedly, you should not collect these or culture them from an area that sprays pesticides (be it you, your neighbors, or your local city, county or municipality), as the mosquitoes often carry some and pass it on to their eggs, which in turn is eaten by the betta when they consume the larvae.

Basically anything that wriggles in the water is going to catch the betta's attention, so find whatever is convenient for you to obtain and give it a try, it's really quite entertain watching bettas and their hunting antics.